Well, in my experience, being totally dark won't suddenly bring the walkaway to their senses. Really, it should be used to help both sides cool off.
She may still be stuck in selfishness mode. There's not much you can do about it. Leave her R with your daughter between them.
Oh...and even if someone did tell her...she wouldn't listen, anyway.
Do you have any reason to speak to her directly about the kids? Holidays, presents, birthdays, anything like that? I'm thinking you need to open up a line of communication with her, even if it's small. Then, you can build on it later.
